假如有两个关联表，是一对多关系的主子表。如下：

主表

CREATE TABLE [dbo].[CourseT](
    [CourseID] [int] IDENTITY(1,1) NOT NULL,
    [CourseName] [nchar](10) COLLATE Chinese_PRC_CI_AS_WS NULL
) ON [PRIMARY]

字表

CREATE TABLE [dbo].[Broad](
    [BroadID] [int] IDENTITY(1,1) NOT NULL,
    [CourseID] [int] NULL,
    [BroadName] [nvarchar](50) COLLATE Chinese_PRC_CI_AS_WS NULL
) ON [PRIMARY]

如果数据取自CourseT表，我们想查询Broad表中记录对应的CourseT表中的记录，且按CourseID的降序只取一次，在SQL2005中SQL如下

with temp as
(
select distinct courseid from Broad
),
 temp2 as
(
    select courseid , ROW_NUMBER() OVER(ORDER BY courseid desc) AS row_num
     from temp
)
select CourseT.* from  CourseT, temp2 where courset.courseid=temp2.courseid order by row_num

如果数据取自CourseT和Broad表，我们想查询Broad表中记录对应的CourseT表中的记录，且按CourseID的降序只取一次，我们可以如下写：

with temp as
(
  select courseid, broadid, row_number() over(order by courseid desc, broadid desc  ) as rownum from broad
),
temp2 as
(
select temp.courseid, temp.broadid from temp where rownum=1
union
select temp.courseid, temp.broadid from temp, temp as temp0 where temp.rownum = temp0.rownum+1 and temp.courseid <> temp0.courseid
)

select CourseT.*, broad.broadid, broad.broadname from  CourseT, broad, temp2
 where courset.courseid=broad.courseid and temp2.courseid = courset.courseid and temp2.broadid = broad.broadid order by
broad.courseid desc ,broad.broadid desc
经牛人宪哥帮忙，又想出一个更好的方案如下：
select CourseT.CourseID,CourseName,b.BroadID,b.BroadName
 from CourseT,broad b,(select max(broadid) bid,CourseID from broad group by courseid ) t
  where
   CourseT.CourseID=b.CourseId and b.CourseID=t.courseid and b.broadid=t.bid
http://www.cnblogs.com/laiwen/archive/2006/12/30/607690.html